In transmissions, engines, single-shaft and gearing compressors, probes can be used for shaft monitoring. Here, a shaft oscillation measurement, a rotational speed measurement or a shaft level measurement is for example carried out. In a broader sense, a probe of said type usually comprises a probe head which is arranged on a probe support and has a measuring sensor for the actual measurement of the measurement values. Said measuring sensor itself is often also referred to in a narrower sense as a probe; The probe support often has a bar-shaped or tube-shaped design, so that it can, even under comparatively restricted spatial conditions, be guided relatively easily through an access opening of a housing which surrounds the shaft to be monitored and can be extracted again from said access opening if required, in particular for servicing purposes. The probe head or the measuring sensor can therefore be placed into its operating position at a point of the housing interior space which is comparatively difficult to access without it being necessary for the housing to be dismantled, or for parts of said housing to be removed, for this purpose.
In order to carry out the measurement as precisely as possible, in particular in order to avoid systematic measurement errors, the measuring sensor must generally be positioned very close to the shaft with a high degree of precision. The permissible tolerance to the nominal distance in the radial or axial direction is often only a fraction of a millimeter. A fastening device for the probe or for the probe support is therefore required which can be precisely adjusted and reliably connected to the housing. A device of said type is generally mounted from the outside after the assembly of the housing or of the machine. Under some circumstances, a retroactive adaptation of the probe position to changed operating conditions of the machine is necessary.
In the case of known probe holders, a screw-in connecting piece is usually screwed with an outer thread into a bore, of the shaft housing, and is fixedly secured on the housing by means of a tube nut. Here, a thread seal can be provided between the tube nut and the housing. The actual measuring probe or measuring sensor is generally arranged here on a support bar which, for assembly, is inserted into the screw-in connecting piece and fixed to the latter by means of a sleeve nut in such a way that the nominal distance of the measuring sensor to the shaft or to the respective object to be measured is approximately reached. Fine adjustment of the arrangement can then be carried out when the tube nut is loosened by rotating the screw-in connecting piece in the threaded bore of the housing wall.
A fundamental problem of the described arrangement is however that the fine adjustment must be carried out again every time the probe has been removed from and re-inserted into the housing for servicing or cleaning purposes or the like. In addition, the adjustment itself is comparatively complex and difficult since, when tightening the tube nut, the screw-in connecting piece itself rotates again out of the previously painstakingly determined nominal position. In the case of machines with a plurality of measuring probes of said type, the time loss associated with the re-adjustment can be considerable. In a machine with 20 measuring probes, said time loss can, for example, be up to a day.
A further disadvantage of said arrangement is that, in the case of a shaft which is mounted in an oil bath, the support bar and the screw-in connecting piece must be produced with high dimensional accuracy with a clearance fit to one another in order to obtain a high impermeability to oil, which is relatively expensive. Sealing problems have however already occurred in the case of this implementation of a probe holder. A further disadvantage of the arrangement is that its range of adjustment is limited by the length of the screw-in connecting piece, so that a plurality of holders can be necessary for using the probe at different measuring points.